Method of spraying closed end cans

ABSTRACT

METHOD AND MEANS FOR COATING THE INTERIOR CYLINDRICAL SURFACE OF OBJECTS SUCH AS METAL CANS FOR FOOD, BEVERAGES AND OTHER SUBSTANCES WHICH NEED PROTECTION AGAINST INJURIOUS REACTION WITH OR POLLUTION FROM CONTACT WITH THE MATERIAL OF THE CAN. RAPID AIRLESS SPRAY COATING OF SUCH SURFACES, WHILE THE SURFACES ARE REVOLVING AT HIGH SPEED, FROM A STATIONARY SPRAY NOZZEL EXTERNAL OF THE CAN, BY PROJECTING A SPRAY HAVING AN ASYMMETRICAL PATTERN INTO THE SINGLE OPEN END OF A CAN HAVING ONE CLOSED END, WITH THE PATTERN OF FLOW EMERGING FROM THE NOZZEL BEING MATCHED TO THE INTERNAL SURFACE CONFIGURATION TO APPLY A UNIFORM COATING. ALSO DISCLOSED ARE SPRAY NOZZELS HAVING THEIR OUTLET ORIFICES DESIGNED TO PROVIDE DESIRABLE SPRAY PATTERNS FOR USE IN THIS METHOD OF SPRAYING, AS WELL AS METHODS FOR MAKING AND SHAPING THE OUTLET ORIFICES.

Oct. 1Q, 1972 w, STUMPHAUZER ETAL 3,697,313

METHOD OF SPRAYING CLOSED END CANS Filed Feb. 24, 1970 4 Sheets-Sheet 1//V VE NT 0R5 L W/LL/AM 0. STUMPHAUZER EDW/N F. H065 TROM ERIC 7: Now32;. E E :1. 31 It; RICHARD E. SCHNE/DER BY ALVIN 4. R000 6% 49M #M i MATTORNEYS 10, 1972 w. c. STUMPHAUZER E A METHOD OF SPRAYING CLOSED ENDCANS 4 Sheets-Sheet 2 Filed Feb. 24, 1970 lA/VE/VTORS W/LL/AM C 5'TUMPHAUZER EDW/N E HOGS'T/POM ER/C r mom I R/CHARD E. SCH/VE/DER Hllliil 5 J 5 BY ALVIN A. R000 5M, M HM i- M ATTORNEYS Oct. 10, 1972 w cSTUMPHAUZER ETAL 3,697,313

METHOD OF SPRAYING CLOSED END CANS Filed Feb. 24, 1970 4 Sheets-Sheet 5WILL/AM c. STUMPHAUZER ER/C 7. NORD R/CHA RD E. SCH/VE/DER J H BY ALV/NA. R000 m E; 15 iww ATTORNEYS Oct. 10, 1972 w, c. STUMPHAUZER ETI'AL3,697,313

METHOD OF SPRAYING CLOSED END CANS 4 Sheets-Sheet 4 Filed Feb. 24, 1970//VVE/V7U/?$ W/LL/AM C. STUMPHAUZER EDW/IV F. HOGSTROM ER/C r. NORDR/CHARD E. SCH/VE/DER BY ALV/IV A. R000 5 1 1W NM v M ATTORNEYS UnitedStates Patent (3" hio Filed Feb. 24, 1970, Ser. No. 13,598 Int. Cl. B44d1/08 US. Cl. 117-96 8 Claims ABSTRACT OF THE DISCLOSURE Method and meansfor coating the interior cylindrical surface of objects such as metalcans for food, beverages and other substances which need protectionagainst injurious reaction with or pollution from contact with thematerial of the can. Rapid airless spray coating of such surfaces, whilethe surfaces are revolving at high speed, from a stationary spray nozzleexternal of the can, by projecting a spray having an asymmetricalpattern into the single open end of a can having one closed end, withthe pattern of flow emerging from the nozzle being matched to theinternal surface configuration to apply a uniform coating. Alsodisclosed are spray nozzles having their outlet orifices designed toprovide desirable spray patterns for use in this method of spraying, aswell as methods for making and shaping the outlet orifices.

BACKGROUND OF THE INVENTION This invention relates to a method and meansfor coating the interiors of cylindrical objects such as metal cans andmore particularly, to an improved method and apparatus for applying auniform coating to the interior surface of a cylindrical container whileone end is open.

Various methods have been proposed for coating the interiors of cansused to contain food, beverages and various liquids or gases to protectthe contents from contact with the can materials. These methods and thecorresponding means have varied to some extent depending upon thecharacteristics of the can to be coated. The prior practices describedbelow and our invention are directed particularly to coating circularcylindrical cans.

In conventional practice metal cans are made in two pieces or in threepieces. In each case one piece is applied in a final operation to closeand seal the can after it has been filled with food or drink. The otherpart of a two-piece can may be a deep drawn cylinder with a closed end.Three-piece cans, so called, comprise open ended cylindrical body shellswith separate top and bottom end discs. One end disc may be coatedsimultaneously with the can body, as a two-piece can. The interior ofthe cylindrical can body is conventionally made of metal and has a seamrunning the length of the can. This seam may be of any common type suchas a lapped seam which is soldered and crimped or cemented, or a buttseam which is welded. The bodies of three-piece cans, instead of beingdrawn from one piece of metal have been made as a double open endcylinder to which an end closure is fastened to seal each end, leaving acircular seam at the joint of the closure and side wall. The end closuremay contain an easy open feature having a pull -tab riveted to thecenter of the cover.

The two or three piece cans with one closed end have heretofore beencoated while being rotated about their own axes, and, using airlessmethods, spraying the in- 3,697,313 Patented Oct. 10, 1972 nozzleprovided a fan-shaped spray pattern distributed so that a maximum amountof pain emerged from the orifice at one end of the fan with the amountof paint decreasing approximately linearly to a minimum amount at theother end of the fan.

A common method of gaging the distribution of flow from a particularnozzle is to spray a short burst of coating material against an upright,vertical substrate with the spray pattern oriented with its long axishorizontal. Typically the substrate contains alternating lands andgrooves, as in a corrugated sheet, to offset the efiect of adverseinfluences such as the blast from the spray gun which can cause washoutor distortion of the true spray pattern. Therefore, the quantity ofcoating material sprayed on any particular area will be reflected by thelength, longer or shorter, of the rivulet in the groove runningvertically downward beneath it.

A particular spray nozzle will reflect its own peculiar characteristicswhen gaged by the above-described method. The known drumhead nozzle hasthe spray pattern, FIG. 10 herein, that is skewed heavily toward oneend. The commonly used prior art, fiat fan, airless paint spray nozzlehas an orifice formed symmetrically with respect to the nozzle axis andslashed with a V- notch through a substantially hemispherical dome downto about the base circle of the dome. Nozzles with such orifices give,and gave, a smoothly distributed, symmetrical spray pattern havingmaximum flow in the middle with gradually diminished flows tapering orfeathering" from the middle to the ends of the pattern. Heretofore therehave been no airless spray nozzles (nor methods of making them) thatprovided desirable asymmetrical spray patterns between the extremes ofthe drumhead and the symmetrical V-notch patterns.

The drumhead nozzles in prior practice was oriented with respect to thecan so that the maximum flow of coating material was directed axiallythe length of the can and the fanshaped pattern was directed toward theradius of the can bottom and one longitudinal line on the side wall fromthe bottom to the open end of the can. This procedure resulted in asubstantially uniform coating being applied over the side wall of thecan; the distribution of the spray fan compensating for the increasingdistance the paint had to travel from the open to the closed end of thecan, but the bottom of the can and the bottom circular seam received anon-uniform coating. The pattern of the drum-head nozzle is such thatthe place of maximum flow of paint had to be directed either at thecircular seam, leaving too little material in the center of the canbottom, or the nozzle had to be directed closer to the center of the endof the can resulting in a deposit, due to centrifugal force, 'ofexcessive paint in the circular seam. The rivet required in thethree-piece can with the easy open or pull tab feature, was particularlydifficult or impossible to coat evenly. The only known remedy for aninadequately coated can was to spray more than enough paint along theside and near the seam to get a desirable minimum coating on the centralpart of the bottom.

Spray coating the interior of the two-piece can or threepiece can withone end closed has also been accomplished in the prior art by an airatomizing or airless spray nozzle mounted on a lance that isreciprocated into and out of the can along its axis while the can isrotated. In the lancing operation the spray may be turned on eitherwhile the lance carrying the nozzle is reciprocated from its innermostposition to the outside of the can, or while moving from an externalposition to the inside of the can, or during reciprocation both into andout of the can.

Several difliculties attend the lancing method. The coating materialtends to be applied to the wall of the can in a helical path which oftenresults in helical streaks along the can wall. Other problems occur intiming the spray with the movement of the lance. -In particular, it isdiflicult to cut off the flow of coating material at the precise instantthat the spray begins to be projected outside the open end of he can asthe lance emerges therefrom while supplying a sufliciently thick coatingto the can wall adjacent the open end. Overspray tends to be excessiveand consequently, maintenance and repair of the reciproeating device andrelated mechanism is often required at frequent intervals. Finally, thelancing method is quite ineflicient in that considerable time isrequired to move the lance into the can and to withdraw it therefrom.

SUMMARY OF THE INVENTION A general object of our invention is to providea method and apparatus for spraying the interiors of hollow cylindricalbodies such as cans having one end open which substantially eliminatesthe disadvantages described above which have been encountered with priorcan spraying methods and apparatus.

Another object is to provide a method and apparatus for spraying theinteriors of cans having one closed end that provides a more uniformfilm distribution, particularly over the closed end and adjacentjuncture with the side of the can.

Another object of our invention is to provide selective outlet orificeshaving form and contour in an airless spray nozzle giving asymmetricalspray patterns selectively related to the relative length and diameterof the can to be coated tending to provide a uniform coating over theentire interior of a can having one closed end. Such a patternpreferably gives maximum flow between one end and the middle of thepattern with smooth gradations from the point of maximum flow to eachend, and an object of our invention is to provide spray patterns whichwill deposit paint uniformly on the sides and ends of the can insubstantial proportion to the relative areas thereof.

Another object is to provide advantageous methods for cutting andforming such orifices in airless spray nozzles to achieve desirableselective distribution in spray patterns throughout a wide rangecommensurate with the range of sizes, shapes and proportions of cans andother hollow objects that need interior coating.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a plan view of the orifice ofone form of of the body of the nozzle of FIG. 1, taken in the plane,

of the line 2-2 of FIG. 1 showing a first cut toward making the nozzleorifice.

FIG. 2a corresponds to FIG. 2, showing however, the second cutindependently of the first cut to illustrate making the nozzle orifice.

FIG. 1a is a view corresponding to FIG. 1 showing the first cut onlytoward making the nozzle orifice.

FIG. 1b is a view corresponding to FIGS. 1 and 1a showing however thesecond cut of making the nozzle orifice, independently however forillustration, of the first cut.

FIG. 3 is a fragmentary view of the cutting edge of one of the wheelsfor ma'king the first cut of the orifice shown in FIGS. 1, 1a and 2.

FIG. 4 is a fragmentary view of the cutting edge of the other wheel forcutting the other part of the orifice shown in FIGS. 1, lb and 2a.

FIG. 5 is a plan view of the orifice of a preferred form ofourcontrolled distribution nozzle.

FIG. 6 is a longitudinal, vertical as viewed, section of the body ofvthe nozzle of FIG. 5 taken in the plane of the line 6-6 of FIG. 7illustrating our preferred method ofcutting this orifice.

FIG. 7 is a top plan view corresponding to FIG. 5, showing, however,steps employed in cutting the finished orifice of FIG. 5.

FIG. 8 illustrates a typical asymmetrical spray pattern obtained fromboth forms of our nozzles illustrated in FIGS. 1 and 5.

FIG. 9 is a top plan view corresponding to FIGS. 1 and 5 showing,however, the form of the orifice of the familiar prior art drumheadnozzle.

FIG. 10 shows the known spray pattern of prior art drumhead nozzles inwhich the place of maximum flow is at or closely adjacent the one endofthe pattern and the place of minimum fiow at the other end.

FIG. 11 is a plan view of the orifice of another preferred form of ourcontrolled distribution nozzle.

FIG. 12 is a longitudinal, vertical as viewed, section of the body ofthe nozzle of FIG. 11 taken in the plane of the line 12-12 of the axisof the nozzle.

FIG. 13 is a view corresponding to FIG. 11, but showing theconfiguration or nominal configuration of both of the cuts or gasheswhich together produce the finished orifice.

FIG. 14 is a fragmentary view of the cutting edge of the wheel formaking the narrower cut or gash.

FIG. 15 is a fragmentary view of the cutting edge of the Wheel formaking the broader cut or gash.

FIG. 16 is substantially a mirror view of FIG. 8 showing the reversed,right to left, pattern of our controlled distribution nozzle of FIG. 11.

FIG. 17 is a fragmentary plan view, partly in section and partlydiagrammatic, of known means for rotating the can, or other hollow body,to be coated interiorly and advanced to a baking oven.

FIG. 18 is a longitudinal section of a hollow body such as a beer canwith one closed end and with an opposite open end through which spray isprojected according to our preferred method of coating the interior ofsuch bodies.

FIG. 19 is a transverse sectional view taken in the plane of the line19-19 of FIG. 18, showing the spray nozzle through the open end of thecan and suggesting the plane of the fan of spray projected into the can.

DESCRIPTION OF THE PREFERRED EMBODIMENTS (A) The controlled distributionnozzle Illustrative and preferred embodiments of our airless spraynozzle orifices for controlled selective distribution spray patterns,are shown in FIGS. 1, 5 and 11 in their final form. The figures relatedto FIGS. 1, 5 and 11 depict the nozzles at various stages of cutting ofthe nozzle orifices, the steps of the methods of making them. It is apurpose of these nozzles to produce fiat, fan-shaped airless spraypatterns having a predetermined distribution which will match ideallywith the internal surface configuration of a can or other hollow body,with a closed end to apply a uniform coating thereover.

In the spray pattern of the controlled distribution nozzle, as shown inFIG. 8, the maximum flow of paint, or coating material, occurs at apoint 10 approximately 75% distant from the far end of the fan F and 25%from the near end. Reasonable tolerances within good commercial practiceare i5%. The amount of material flowing in the rest of the fan taperssmoothly and substantially linearly from the point of maximum flow 10,to points of minimum flow at each end of the fan. In contrast, the priorart drumhead nozzle, FIG. 9, produced the familiar fan pattern, FIG. 10with maximum flow at the point 11 at or quite closely adjacent one endof the pattern and tapering linearly to minimum flow at the other end;substantially in a %-5% flow distribution.

(B) First nozzle embodiment An illustrative embodiment of a controlleddistribution nozzle adapted to produce a spray pattern with adistribution similar to FIG. 8, is illustrated in FIG. 1, and comprisesan orifice O slashed or cut in the top as viewed, of the hollowcylindrical body B, the workpiece until completed, FIGS. 2 and 2a, withan internal cylindrical approach passage P terminating in the plane 36,its upper end in the base circle, or eclipse, of a substantiallyhemispherical internal dome D. The wall of body B is, for convenientillustration, shown to be of substantially uniform thickness over andabout the dome. The orifice O is of size, shape and position tending toyield a distribution profile similar to FIG. 8, and is cut into the domeD by two rotary cutting wheels, W and W having different cutting angles,i.e., different degrees of peripheral sharpness, FIGS. 3 and 4. Thewheels may have appropriate known qualities for coping with the materialof the nozzle tip.

A first rotary cutter, such as a diamond charged wheel W, FIG. 3, andsee FIG. 1a, for cutting tungsten carbide, is narrowly tapered with anincluded angle of about 22 /2 at and comprising the cutting edge. It mayhave a radius R of 3 inches, for example, to cut the narrow, leftward,as viewed, part of orifice 0, FIGS. 1, 1a and 2. The wheel W has itscenter angled leftwardly from the longitudinal axis aa of the body B,and cuts an inclined tapered gash along and down to the line 37 throughthe wall of the body above and adjacent the dome D down to the leftwardpoint x at the base circle of the dome and down to the point x above thebase circle on the right side of the dome as shown in FIGS. 1a and 2.The line of the bottom of the cut 37 is angled to the base of the domeand the inclined aspect of the wheel to the axis a-a of the paS- sage Pbeing for this example 7 /z as shown.

In this illustration the movement of the Wheel W, as well as W discussedbelow, will be in the plane 2-2 of the axis aa. A 3 inch wheel cuttingan orifice .015 inch long, for example, will have a substantiallystraight line 37 for the bottom of the cut even if the bodily movementof the center of the wheel advances the wheel only along its radius R onthe line 45, 41, 43 inclined at said 7 /2" to the axis aa. The line45-43 is the perpendicular bisector of the line 37 between the points xand x and passes through the center of the base circle of the dome, i.e.the intersection of a-a and plane 36 normal thereto. The same cut may bemade with inclined rightward and leftward bodily movement of the wheelso long as the 7 /2 inclined aspect of the wheel to the work ispreserved.

In this illustration the cuts or gashes made by the wheels W and Wrespectively, are shown in FIGS. 2, 2a, 1a and 1b as if each were afirst cut. In practice the cuts are made successively so the second cutis made in part in the void of the first cut and is more awkward toexplain in the first instance than the fiction of each cut being firstand original. In FIGS. 1, 1a and lb the circle, or eclipse of the baseof the dome is suggested in dotted lines. As shown in FIG. 2, the line37 intersects the outside of the body at points 39 and 49 which definethe ends of the gash in the exterior of the body. Points 45 and 41 showthe places of greatest width of the cut at the outside and inside,respectively, of the wall of the dome, and are offset from the axis bydistances 44 and 40 respectively. Vertical projections of points 41 and45 intersect the diameter of the base of the dome in points 42 and 46respectively. The equivalent of points 41, 43 and 45 in the wheel W whencutting at full depth on the line 37 are shown at points 41a, 43a and45a respectively in the wheel whereby to visualize the maximum widths 48and 47 of the gash in the exterior and interior of the wall of the dome.These lines of width are transposed to FIG. 1a passing through thepoints 46 and 42 respectively and show the effect of tipping the gashand moving the places of maximum width leftwardly of the axis aa. Asseen in FIG. 1, this leftward inclination of 0' makes the widest part ofit join the gash 0", FIG. 1b, more harmoniously than were the line 37 tolie in the plane 36. This also results in a smoother line from the pointin FIG. 8 to the left end of the spray pattern. This inclination of the6 line 37 tends in minor degree to move the point 10 leftward in thespray pattern, of FIG. 8.

A second cutting wheel W of greater included angle of taper in thecutting edge, taken arbitrarily at 50 for this illustration, and radiusR, FIG. 2 equal to R has its center offset rightwardly from the axis aaof body B, and cuts a broader rightward gash 0 through the dome, thebottom line 61 of which is inclined at 30", also taken arbitrarily, tothe axis and plane 36. Wheel W cuts through the wall above and about thedome D down to the point y on the right of the base circle of the domediametrically opposite the point x. This puts the ends of the exteriorof the cut at the points 59 and 60 as shown in FIGS. 2a and lb, and putsthe actual and tentative ends of the part 0" of the orifice O at thepoints y and y in the surface of the dome. When this is literally asecond cut, the points y and 59 will lie in the void of the left wardpart of the first cut. Following the procedure used above, theperpendicular bisector of the part y'-y of the line 60 originates atpoint 53 and passes through the intersec'tion of the axis and plane 36and the points 51 and 55 in the dome and external wall above it. Thesepoints are offset distances 50 and 54 respectively from the axis andproject downwardly to points 52 and y in the diameter of the base of thedome. Transposition of corresponding points 53a, 51a and 55a in thewheel W, FIG. 4, permits the measurement of maximum width of the cut inthe dome and in the wall above it at lines 57 and 58, the transpositionof which to FIG. 1b depicts the whole cut and orifice containing thepart 0" in plan view, as if the cut were made through solid material inthe first instance. It remains merely to superpose FIGS. 1a and 1b toshow the effect of the successive steps and cuts to make the compositeorifice O and the exposed surfaces of the cut in the wall above andabout the dome. The orifice O has sharp cusp at both ends. Particularlythe right, as viewed, end which distinguishes it radically from theprior drumhead nozzles, and provides smoothly curved lines joining theplace of maximum flow, corresponding to the point 10, to the ends of thepattern. The line 57 of greatest width of the orifice 0 correspondsapproximately with the place of greatest flow in the pattern, and by itslength and offset from the axis a-a plays the major part in placing thepoint of maximum flow, like point 10, where it may be desired in thespray pattern.

In FIG. 8, the oval area F at the top of the pattern is the place ortarget of impact of the fan F with the corrugated sheet or substrate.The point 10 lies at the bottom of the longest line of fiow of paintfrom the oval and shows the whereabouts in the spray fan of maximumflow. The lesser lines of flow of paint from different parts of the ovaldown the sheet measure the relatively lesser quantities of paint incorresponding parts of the fan. We have called the part H of the patternto the left of the line of point 10 the heavy part, and the part L tofl1e right, the light or lighter part. This is convenient in respect torelating the different parts of the pattern to different parts of thecan or hollow body being painted. This explanation is made to avoidconfusion between one usage and the logical description of the heavypart of the pattern as that containing the maximum flow. In our usage wespeak of the line or path of maximum flow as the line of divisionbetween parts H and L, or as an appreciable part of the patterncomprising the great flow to the point 10, as the context will suggest.

The following description of our two preferred forms of nozzle orificeswill exemplify different advantageous ways of following the principlewhile altering the form of the orifice 0 described above. Preliminarily,it will be evident from the discussion about the orifice O that reducingthe inclination of the line 60 from 30 to 20 about the point y, forexample, that the wide cut from the wheel W will be extended leftward,tending to move the point 10 leftward in the fan pattern, and increasingthe light part L of the pattern at the expense of the heavy part H. Thiswill also tend to lengthen the cusp up from the point y and improve thequality of distribution in the part L of the pattern. Foreshadowing ourpreferred orifice in FIG. 11 (which is turned right for left from FIGS.1 and 5), our teaching includes changing the depth as well as theinclination of any cut through the dome; specifically-raising and/ortipping the bottom line 60 of the cut, to diminsh the size and effect ofo"- in relation to in the orifice O.

(C) The first preferred nozzle A first preferred embodiment of ourcontrolled distribution, or controlled pattern, nozzle is shown in FIGS.5, 6 and 7,'and differs from the embodiment described above in both theshape of the discharge orifice and in the method of cutting it. As shownin FIG. 5, the orifice O0 is approximately tulip-shaped, orarrowhead-shaped, comprising two minor divergent cusped lobes 23 and 24on the right as viewed, side of the axis aa of nozzle body B which mergeinto a major cusped lobe that terminates at the point x, see also FIGS.6 and 7, on the opposite side of axis aa. The lobes 23 and 24 join atthe point 34, or line 34-35, diametrically opposite the point x buthigher on the curve of the dome from the base thereof, FIGS. and 6. Thesection of maximum width 28 of the orifice lies near the point 34substantially in a plane at right angles to theplane containing the axisand points x, 34 and 35. Approximately 25% of the coating materialoutput from the orifice 00 appears to emerge from lobes 23 and 24 whileabout 75% of the material appears to emerge from the remaining portionof the orifice to form the spray pattern of FIG. 8.

The tulip or arrowhead orifice 00, FIG. 5 is preferably cut and formedas shown in FIGS. 6 and 7 by the cutting wheel W2 making two chordalgashes down to the base circleof the dome; both gashes passing throughthe point x on the left, as viewed, with one passing through the point yand the other through y on the right side of the base circle of thedome. The first cut is shown in full; the second in dotted lines in FIG.7. The bottom of the first out and the intersection of the central planethereof with the plane of the base circle of the dome follows theimaginary line K, FIG. 7, at the angle 0 from the central longitudinalplane 6-6of the body B. After the first cut is made the work piece, i.e.the unfinished body B, is rotated relative to the wheel W about a lineparallel to axis aa andvpassing through the point x so that the secondcut will follow the line Q at an equal and opposite angle 0 on theopposite side of the central plane 66. The second cut is shown in dottedlines; the two gashes together form the arrowhead orifice 00, FIG. 5.The finished orifice 00 has major sloping side surfaces 30' and 31 andminor side surfaces 32 and 33 which lie on opposite sides of the uncutwedge-like part 38 of the wall ofthe dome. The surfaces 32 and 33intersect in the line 34-35 in the plane 66, FIG. 7. It will beappreciated that when the lines K and Q coincide a simple symmetricalpattern will result and the point like of maximum flow will be shiftedto the middle of the pattern. Conversely as the angle of divergence 2cbetween lines K and Q increases, the point of maximum flow will be movedmore nearly to the right, as viewed, in FIG. 8, of the pattern.Presently we have not tested the advantageous limits of such divergencebeyond shifting the point 10 to about an 85 pattern.

An example of a controlled distribution nozzle formed in this manner hasan orifice of about .015 inch equivalent diameter and projects a fanspray having an output rate of flow of water of about 120 cc. per minuteat about 40 p.s.i. The width of the fan-shaped spray pattern produced bythis orifice is approximately 8-10 inches measured normal to the nozzleaxis at about 10 inches from the nozzle to the target. The cutting edgeof wheel W2 is tapered at an included angle of about 25 and has a radiusof 3 inches. Angle c in FIG. 7 is approximately 8 /2 (D) The secondpreferred nozzle This preferred form of our nozzle invention and methodof making an embodiment thereof is illustrated in FIGS. 11-15. Anillustrative spray pattern from this nozzle is shown in FIG. 16, whichis a mirror view of FIG. 8. The orifice 03, FIG. 11, is a compositeresulting from two successive cuts made by two different Wheels W3 andW4, FIGS. 14 and 15, both moving in the central longitudinal plane 1212and making cuts of different inclination, breadth and depth.

As shown in FIGS. 12 and 15, and in full lines in FIG. 13, this firstcut is quite conventional and made with the wheel W3 having a cuttingedge with faces inclined at a 37 included angle, down to the line 70 inplane 36 of the base of the dome at the orthodox points x and y. Such acut would give a conventional symmetrical fan pattern as if the point 10were in the middle. The center of wheel W3 is aligned with the axis aaof the dome D, approach passage P and nozzle body B, so the line 70 ishorizontal and the perpendicular bisector of x-y coincides with the axisaa. The widest part of the cut through the dome is suggested at 75 andthrough the outer wall at 76, FIG. 12, and translates to lines 75b and76b taken through the wheel W3 at points 75a and 76a, correspondingpoints 75 and 76 in the work, and to the cut as viewed in plan and seenin full lines in FIG. 13. The line 70 of the first cut crosses the axisaa at point 72, FIG. 12, as suggested at the point 72a at the extremeedge of the wheel, FIG. 14.

The second cut has the orifice and function of moving the line or pathof greatest flow in the spray pattern from the middle leftwardly asviewed in FIG. 16 over to about the quarter point about midway betweenthe center and left end of the pattern and giving the light side L about25 and the heavy side H about 75 of the flow of paint. This second cutis made with the wide (115) angle cutting edge wheel W4, FIG. 15,inclined along line 71 at 16% to the plane 36 and line 70 with thecenter of the wheel angled 16 /2" from axis w-a when it coincides withthe perpendicular bisector 72-74 of the part 77 79 of line 71 where thelatter intersects the hemisphere of the'dome, actually in the voidinvthefirst cut. The bottom of the second cut at its greatest depth reachesonly about 40% of the way down the radius 7273 of the dome whence theextreme ends of the first cut in the plane 36, FIGS. 11, 12 and 13, areuntouched by the wheel W4,

and their narrow sharp cuspcd ends persist in their benign influence atand within the edges of the parts H and L of the spray pattern.

Projecting the points 77, 74, 73, 79 and the intersection of line 71with the outside of the wall of the dome down in the plane 1212 to thediametric line x-y and 70, the respective points 87, 84, 83, 89 and 71aare established to locate these points in plan view in FIGS. 11 and 13.The projection of the. intersection of line 71 with the left interiorsurface of the dome is substantially coincident with the intersection ofthe line 70 with the same surface. These projected points locate theends and places of greatest width of the orifice and gash cut by thewheel W4. The respective widths are found, as above, by translating thepoints 73 and 74 into the wheel at points 73a and 74a; the point 78atranslating extreme edge of the wheel contacting the point 78. At thepoints 73a and 74a in the wheel, the width thereof, which reflects themaximum width of the orifice and gash is shown in lines 73b and 74b, andtranslating these lines into FIG. 13 establishes the plan view of theoutline, shown in dotted lines, of the gash through the wall above thedome and the orifice in the dome.

As shown in FIGS. 11 and 13, the bluntness of the wheel W4 make thegash, and orifice cut thereby, almost as wide as long and loses thetheoretical ends of the orifice in the void of the first cut. In FIG.11, the dominance of the part 91, of the final orifice 03, made by thewheel W4 is shown realtive to the part 90 cut by the wheel W3 in theright part of orifice O3, and a small part of the orifice and gash cutby the wheel W3 at the left end of the orifice 03, FIGS. 11 and 13.

Our present tests and observation of nozzles having the orifice 03appear to show that their orifice can give much the same pattern, FIG.16, as the nozzle '00, FIG. 8, when the place of maximum flow, point 10,is midway between the middle and the near end of the pattern. The nozzle03 presently appears to be more predictable in respect to its pattern asthe second cut is inclined, and/or cut more deeply, to move the point 10of the pattern nearer the end of the pattern. Conversely reducing theinclination of the second cut, as from 16 /2 to 13 will tend to move thepoint 10 of the pattern toward the middle, reducing H and increasingI...

-(E) The method of coating generally In FIGS. 17, 18 and 19, ourpreferred method of coating the interiors of hollow bodies, like cans,is illustrated. The cans to be coated must be indexed one by one to aspraying station where they are revolved rapidly, by known mechanism asin the Eberhart, US. Pat. No. 2,189,- 783, and sprayed by a stationaryautomatic airless spray gun and our nozzle. The cans, still rotating,are then dropped or stepped out of the indexing apparatus to an inclinedbelt or chute on which they continue to rotate and roll to a bakingoven. The belt and/or chute is of a length and inclination such that thecans will roll for a suflicient time and for a suflicient number ofrevolutions to allow the coating to become so tacky that it will nolonger flow, and therefore not impair the uniformity of coating obtainedduring spraying, before the coating is fixed by baking. The cans thenare moved into the oven where the coating is baked at a prescribedtemperature for a proper time. Illustrative can indexing and rotatingapparatus is suggested diagrammatically in FIG. 17.

Preferably, the spraying of the can interiors should result in a uniformfilm distribution with a weight of coating of a particular number ofmilligrams per square inch according to prescribed specificationsrelated to the use and proposed contents of the can. Coating materialsmay be vinyl, epoxy, butoxy, phenolic, acrylic, alkyd, modifications ofthe above, or other suitable coatings.

Film distribution is commonly determined electrically by measuring theresistance of the film at a plurality of points on the interior surfaceof the can. A method of determining overspray is to measure the weightgain of the can and the weight of oversprayed material which is captureduring the spraying process. The captured overspray material then may becalculated as a percentage of the total weight of the material emergingfrom the nozzle.

In FIG. 17, an illustrative can indexing and rotating apparatus 1 isshown rotating a can C having one closed end 7 at a spraying stationwhere gun G with nozzle N is positioned at the open end of the can tospray and coat the interior thereof, see also FIGS. 18 and 19'. Nozzle Nis oriented with respect to the longitudinal axis ss of the can, itsdirection of rotation and the intended line and angle of contact of thespray fan with the inside of the can to provide the very rapid coatingof uniform thickness discussed more fully below. Nozzle N and automaticgun G therefore is rotatably, pivotally and adjustably mounted onindexing table 2 which allows the nozzle to be positioned bodily andaimed about horizontal and vertical axes with respect to the interior ofthe can to be coated. Appropriate hoses, not shown, supply paint atdesired temperatures and pressures to the Each can is rotated in adirection that advances the exposed edge of the lapped joint 17 of thecan to receive head-on a tangential component of a spray fan, FIG. 19.The can is rotated at high speed, characteristically between 500 and3000 revolutions per minute, a typical example being 1 650 r.p.m. Thecoating material is sprayed into the interior of the can during a littlemore than three revolutions; e.g. for about to 200 milliseconds. Auniform coating of desired thickness, for example, 3.5 to 6-.5milligrams per square inch is deposited in this short time. The coatingmaterial has advantageously, properties of good wettability andadhesion. Viscosity is characteristically Within a range of 14 to 40seconds as measured with a Zahn No. 2 efilux cup at 77 F. The coating isdeliberately sprayed olf the proximate edge 16 of the can for a distanceof, for example, about V to insure full coating thickness to and on theedge.

Immediately after each can is coated and while still rotating, it isstepped forward to a releasing station general-1y indicated as 3, FIG.17, where it is released from the rotating and indexing apparatus andcaused to roll down a long inclined ohute 4 at a rate of rotation thatprevents the still mobile coating material from moving its place ofuniformdeposition.

Continuing rotation causes the material to set with uniform thicknessbefore baking. The length of the inclined chute 4 is much greater thanshown in FIG. 17, and is such that the can is caused to make a generousminimum number of setting revolutions, fifty for example, during whichthe paint becomes tacky so that it will not flow. At the same time somevolatiles have time to escape the can 'before it enters the baking oven.At the end of inclined chute 4 the can may enter the oven 5 where thepaint is baked at a prescribed temperature; e.g. at 300 F. for about 6minutes, sufircient to cure and harden the applied film of theparticular coating material.

(F) Coating cans with a single open end The internal surface of a singleopen end can is coated, as shown diagrammatically in FIGS. 17 to 19 witha spray gun employing our novel controlled distribution nozzle,preferably having the orifice form of FIG. 5 or 11. Only one nozzle N isemployed, the axis n of which is positioned to spray into the open endwith the fan F at a small angle 1, FIG. 19, measured horizontally withrespect to the vertical plane v of the longitudinal axis s-s of canbody, and with axis n of the nozzle at an angle e, FIG. 18 measuredvertically with respect to the horizontal plane h, of the axis of thecan body. The nozzle orifice is located a distance 18 from the open endof the can, FIG. 18 and about half that distance about the plane I: andenough to the left of v to provide the angle 1, FIG. 19. Consequentlythe line 6 of maximum flow in the spray fan (see point 10 of FIGS. 8 and16), is intended to be directed at the circle of intersection betweenthe closed end 7 of the can and its cylindrical side 8. The heavyportion H of the fan is directed along the side of the can body whilethe lighter part L is directed toward the closed end 7 of the can. Thewidth and direction of the fan shaped pattern from the nozzle orifice issuch that the outside edge 9 of the lighter portion L of the fan isdirected at the center of the circular bottom or closed end of the can,and the opposite edge 15 of the fan is directed at, or very slightlywithout, the edge 16 of the open end of the can.

With this orientation the distribution pattern of the spray nozzle isideally matched to the areas and portion of the internal surfaces of thecan to be coated. The heavy part H of the fan spray falling between theopen edge 16 of the can, and the closed bottom end 7 provides a uniformcoating on the sidewall 8, all portions of which are rotating at thesame lineal speed. The lighter portion L of the spray fan decreases froma maximum flow along the line 6 to a minimum desirable flow at the outeredge 9 of the spray fan which is directed at or slightly beyond the deadcenter of the circular closure end 7. The amount of coating materialapplied to can end 7 is greater at the places further from the center sothat the amount of coating material decreases with the decreasing radiusof can end 7 to the dead center thereof.

Our method is premised on, and permits the novel matching of the spraypattern to the shape and proportion of the interior of the can. Shouldthe area of the bottom of the can be one-third the size of the area ofthe side, our method would employ a nozzle giving a theoretical 25%-75%pattern with A of the flow of coating material in the part L and in thepart H, FIG. 18, having in mind, however, our collateral teaching that(1) the seam 19 needs a controlled quantity of paint more than enough tocover a pure geometric circle, (2) the rivet and die cut in pull-tab endclosures may need paint more than normal smooth surfaces, '(3)centrifugal force tends to wash mobile, wet paint off the end closure,(4) a little overspray must be lost from part H at the open end of thecan and (5) the effusion of solvents from the fan and target areaprobably impair the flow of paint to the closed end more than to theside of the can. Depending on the ratio of can length to diameter, amongother things, our present experience suggests that these collateralconsiderations may make a 25%-75% pattern advantageous in a can having aclosed end of noticeably less than 25% of the whole internal area and aside wall area correspondingly greater than 76% the total area.

The fact that a prior art drumhead nozzle would serve to coat the insideof a very long can of small diameter, and a conventional nozzle with asymmetrical pattern would coat a shallow can of large diameter, bottomarea about equal to side area, does not diminish the advantage andeconomy of our method and means for coating the interiors of cans whoseproportions lie between these extremes.

In contrastwith prior practice of using the prior drumhead nozzle tospray the sidewall and end of such a can, our controlled distributionnozzle puts substantially equal, desirably minimum, quantities of painton every square inch of the whole interior surface in the firstinstance. When the circle of juncture between the side and closed bottomof the can comprises also a seam 19 that may have raw edges and minutevoids, our nozzle and method puts the maximum flow right on the circleand seam whereour selected distribution and pattern insures propercovering'of the seam without the hazard of flooding the annular corner.

The proportions of the can also influence the most advantageous locationof the nozzle N, the inclination of its axis ss and the disposition ofthe fan in relation to the interior of the can. A preferred position ofnozzle N is off the axis ss of can C as shown in FIGS. 18 and 19. Whenthe can is rotated clockwise, as viewed in FIG. 19 and suggested by thearrow, the spray fan F is inclined at angle 1 to have a tangentialcomponent where it meets the side of the can to meet the raw leadingedge of the lap seam 17 head-on whereby to insure a proper covering ofthe edge, and voids, if any, in the lap, of the seam with ample coatingmaterial.

While we have mentioned our preference for particular speeds of rotationof typical cans while the coating spray is being applied, we also preferthat the can be rotated no less than a whole revolution, obviously, andalso that the can be rotated a whole number of revolutions plusafraction of a revolution corresponding to the circumferential distancethe can rotates while the flow from the nozzle builds up from zero tofull-flow, and vice-versa, i.e. while the valve in the paint gun ismoving from closed to open, and vice-versa. ,With a solenoid actuatedpneumatically operated valve the time taken for valve opening andclosing is small but long enough to permit the rapidly moving coatedsurface to move an appreciable distance and .be covered with acircumferential wedge of coating of increasing depth while the valve isopening, and, desirably, should be covered with an equal and oppositewedge of decreasing depth while the valve is closing. The same problemand same solution pertain to the end wall as to the side wall of thecan. Our teaching is to effect the overlap as fully as practicable, asprecise 12 timing will suggest and examination of a few trial runs willcheck. It will also occur to those skilled in the art that-imperfectionor omission of the overlap will diminish in importance as the number ofpainting revolutions and coatings increase beyond the first ones.

(G) Example of spray coating single open end can According to ourpreferred method of spraying the single open end can C, nozzle N waspositioned with its axis n at an angle 2 of 43 with respect to plane h,and at an angle f of 0 the axis lying in the vertical plane v. Thedistance 18 from the nozzle N to the plane of the can opening, FIG. 18,was about inch. The nozzle N was located about twice as high above planeh as that shown in FIGS. 18 and 19 to be about 5 inch from the top edgeof can C and, correspondingly, inclined more steeply; maximum flow alongline 6,'FIG. 18, still was aimed at the circular seam as shown.

The can C was about 2 inches in diameter and 4 inches long. The nozzleflowed 208 cc. of water per minute at 40 p.s.i. and gave a distributionpattern at 10. inches distance of 74.5%25.5%, H to L with a fan widthbetween 10 inches and 10% inches. In this example the paint was sprayedat 700 p.s.i., and -140 F. The spray was turned on for 167 millisecondswhile the can was rotating at 1650 r.p.m. The coating material waslacquer reduced in a 1 to 1 ratio with a suitable solvent such as MIBK(methyl-isobutyl-ketone) and xylene to a viscosity of 23 secondsmeasured with a Zahn No. 2 cup at 77 F. After spraying and coating, thecan was released from the spraying station and continued to be rotatedand rolled for about two minutes at 250 r.p.m., and low velocity air wasmoved through the can to remove solvent vapor during the second minutebefore delivery to the baking oven. In the oven the can was baked forabout 6 minutes at a temperature of 300 F. Before the can was formedthemetal had been precoated to a thickness of 4 milligrams per square inch.The material which we added by spraying was 5.9 milligrams per squareinch so that the total coating thickness was 6.3 milligrams per squareinch. Maximum variation in thickness was measured as 1.2 milligrams persquare inch.

While we have illustrated and described exemplary and preferred forms ofour invention, changes and improvements will occur to those skilled inthe art who understand its advantages and uses, and we do not want to belimited to the embodiments and examples specifically disclosed herein,nor in any manner inconsistent with the progress by which we havepromoted the art.

What we claim is:

1. The method of coating the interior of one end surface and the innercylindrical surface of a body having a longitudinal axis and one openend with a peripheral edge and having one circular closed end surfacenormal to said axis, comprising rotating said body about its said axis,projecting an airless spray fan of liquid coating material from a fixednozzle having a central axis into said rotating body through the openend thereof, providing said fan with an asymmetrical pattern with thepoint of maximum flow about midway bewteen the middle of said patternand one end thereof, aiming said fan into said body with said point ofmaximum flow substantially contacting the junction of said closed endand said cylindrical surface.

2. The method of claim 1 with the step of placing said fan in a chordalplane parallel with and spaced from the axis of said body and on theside of said axis which directs paint into contact with said cylindricalsurface with a tangential component moving opposite the direction ofmovement of said surface.

3. The method of claim 2 with the axes of said nozzle and bodyrespectively appearing to intersect at an acute angle when viewed atright angles to said fan.-

4. The method of claim 1 wherein the pattern of said fan provides thegreater flow between said place of maximum fflow and one end of saidpattern herein called the heavy part of the fan, and places the lesserflow between said place of maximum flow and the other end of saidpattern, herein called the light part of the fan, with the step ofdirecting the heavy part to the surface of greater area and directingthe lesser part to the surface of lesser area.

5. The method of claim 4 with the step of proportioning said heavy andlesser parts to deposit coating material at uniform depth through allsurface areas of the body.

6. The method of claim 5 with the step of diverting more than theproportionate share between said heavy and light parts based on relativeareas to the light part when the light part is directed toward theclosed end of the body and the closed end is of markedly less area thanthe side of the body.

7. The method of claim 1 With the steps of directing one point ofminimum flow in said pattern at about the center of said closed end anddirecting the other point of minimum flow slightly outside the edge ofthe open end of said body.

References Cited UNITED STATES PATENTS 3,259,673 7/1966 Ericson117-105.1 3,445,262 5/1969 Greek et a1 118-302 X 2,048,912 7/1936 Ziskaet al 118-302 EDWARD G. WHITBY, Primary Examiner US. Cl. X.R.

29-157 C; 117-97, 105.4, 161 'UZ, 161 ZB, 161 K; 118-318; 239-601

